I just got a 2010 Camaro and the temp guage will not read but I have an error saying ac off due to high engine temp, it doesn't give it every time I drive it but it's often. I'm pretty sure the thermostat is leaking and am going to replace it. I have a plug in obd2 reader that will clear codes and when I do everything looks ok for a few seconds but will immediately go back to the error. It says to follow owners manual for adding coolant but mine is missing and I can't find instructions online. I also have p0017 and p0008 codes along with misfires but not sure if that's related.